Suspected Abu Sayyaf militants have freed three abducted aid workers in the southern Philippines after the government withheld antipoverty funds, prompting an impoverished town to pressure the rebels to release the captives, officials said Wednesday.

Social Welfare Secretary Corazon Soliman said the three aid workers and a companion were kidnapped last Thursday in remote Talipao town in Sulu province where they were checking on families who could receive the aid and working on another antipoverty project.

Due to the kidnappings, the government withheld the cash grants to thousands of poor families to ensure the safety of aid workers. Talipao officials then exerted pressure on the militants, who freed their hostages this week without any ransom payment, Soliman said.

"We didn't want to put anyone else in a very risky situation," she said.

Soliman said town officials negotiated with the gunmen to free the hostages.

A military official said armed relatives of one of the kidnapped workers threatened the family of an Abu Sayyaf militant, helping to ratchet up pressure on the kidnappers. More than 4 million families across the Philippines have received cash under a government program that requires the "poorest of the poor" to get regular medical check-ups and ensure their children attend school classes in exchange for financial aid.

Sulu, about 590 miles south of Manila, is one of the country's poorest provinces.

The Abu Sayyaf, which has about 300 armed fighters split into several factions, was organized in the early 1990s in the south and vowed to wage jihad, or holy war, but the early combat deaths of its key commanders sent the group on a path of criminality. It has been crippled by government operations but endures largely due to huge ransoms from kidnappings.

Abu Sayyaf now holds about 10 hostages, including two German tourists seized in April and two birdwatchers, one Dutch and the other Swiss, who were kidnapped two years ago.

Malaysia, meanwhile, has imposed a dusk-to-dawn curfew in waters near six districts in Sabah state on Borneo Island where Abu Sayyaf gunmen from the southern Philippines have staged nighttime kidnappings.